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For the case of the uniaxial section, moment-curvature and axial force-deformation curves are defined independently, and numerically.
For the case of the fiber sections (steel and RC), uniaxial materials are defined numerically (stress-strain relationship) and are combined into a fiber section where moment-curvature and axial force-deformation characteristics and their interaction are calculated computationally.
While this distinction does not affect the section definition itself, it affects the degree-of-freedom associated with moment and curvature in the subsequent analysis.
There are two differences between the two models:
1. The space defined with the model command (# Define the model builder, ndm=#dimension, ndf=#dofs) |
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2D: |
model BasicBuilder -ndm 2 -ndf 3; |
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3D: |
model BasicBuilder -ndm 3 -ndf 6; |
2. In the 3D model, torsional stiffness needs to be aggregated to the section |
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Uniaxial Section |
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Flexure and axial behavior are uncoupled in this type of section |
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Fiber Steel W SectionCoupled biaxial flexure and axial behavior |
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Fiber Reinforced Concrete SectionCoupled biaxial flexure and axial behavior |
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Rectangular Symmetric Section, Unconfined Concrete
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Rectangular Symmetric Section, Confined Concrete Core
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Rectangular Section generic rectangular section
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Circular Section, Confined Core
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